如何在R中的geom_segment/ggplot2中绘制定向蜘蛛网络？

Question

我正试图通过方向绘制所谓的spider network或者desire line说明特定区域之间的事物(人,车辆等)的运动.

这是我正在使用的数据框:

df <- data.frame(O=c(1,2,4,4,4,6,6,6,7,7,7,9,9,9,9,10,10,10,11,12,12,12,32,86,108,128,128,157,157,157,157,157),
D=c(2,1,6,7,32,4,7,157,4,6,157,10,11,12,157,9,12,157,9,9,10,157,4,128,128,86,108,6,7,9,10,12),
trip=c(971,971,416,621,330,416,620,1134,621,620,625,675,675,378,439,675,724,472,675,378,724,563,330,610,405,610,405,1134,625,439,472,563),
lon.x=c(697746.6,696929.6,696748.8,696748.8,696748.8,694906.4,694906.4,694906.4,696769.4,696769.4,696769.4,698802.2,698802.2,698802.2,698802.2,698900.5,698900.5,698900.5,699686.7,696822.0,696822.0,696822.0,698250.7,702314.7,700907.1,702839.5,702839.5,694518.9,694518.9,694518.9,694518.9,694518.9),
lat.x=c(9312405,9311051,9308338,9308338,9308338,9307087,9307087,9307087,9305947,9305947,9305947,9304338,9304338,9304338,9304338,9302314,9302314,9302314,9306300,9303080,9303080,9303080,9309423,9320738,9321302,9322619,9322619,9301921,9301921,9301921,9301921,9301921),
lon.y=c(696929.6,697746.6,694906.4,696769.4,698250.7,696748.8,696769.4,694518.9,696748.8,694906.4,694518.9,698900.5,699686.7,696822.0,694518.9,698802.2,696822.0,694518.9,698802.2,698802.2,698900.5,694518.9,696748.8,702839.5,702839.5,702314.7,700907.1,694906.4,696769.4,698802.2,698900.5,696822.0),
lat.y=c(9311051,9312405,9307087,9305947,9309423,9308338,9305947,9301921,9308338,9307087,9301921,9302314,9306300,9303080,9301921,9304338,9303080,9301921,9304338,9304338,9302314,9301921,9308338,9322619,9322619,9320738,9321302,9307087,9305947,9304338,9302314,9303080))

df包括以下字段:
O:旅行的起源
D:旅行的目的地
trip:之间出游的人数O和D
lon.x原产区的经度:
lat.x:原产区的lattitude
lon.y:目标区域的经度
lat.y:目标区域的lattitude

目前,我可以得出以下使用这里的脚本图geom_segment中的ggplot2包:

library(ggplot2)

ggplot() +
  geom_segment(data = df, aes(x = lon.x, y = lat.x, xend = lon.y, yend = lat.y, size = trip),
               color = "blue", alpha = 0.5, show.legend = TRUE,
               position = position_dodge2(width = 100)) +
 scale_size_continuous(range = c(0, 5), breaks = c(300, 600, 900, 1200),
                       limits = c(100, 1200), name = "Person trips/day (over 100 trips)") +
 theme(legend.key = element_rect(colour = "transparent", fill = alpha("black", 0))) + 
 guides(size = guide_legend(override.aes = list(alpha = 1.0))) +
 geom_point(data = df, aes(x = lon.x, y = lat.x), pch = 16, size = 2.4)

问题是,从每一行O到D和D到O重叠.我更愿意根据中心线绘制躲避的段,以正确显示总行程数并查看区域对之间的行程平衡.

所需结果的一个例子如下所示.

虚线中心线不一定显示(我只是用它来显示平衡是什么).还优选通过方向改变颜色,例如,顺时针方向为红色,逆时针方向为蓝色.如果方向可以用颜色显示,则不需要箭头.

我找到了一些解决问题的例子,但此时我无法达到理想的结果.

坐标偏移的计算
在这个例子中为每个方向设置偏移并不是那么容易,因为我有大约80个区域,这导致了6,400对区域. 在ggplot中偏移geom_segment

position_dodge2函数
它说我可以在width使用变量的段之间设置边距,但是如果我使用trip它,它会返回错误.此外,我不清楚应该为适当的偏移设置多少值,以使分段跟随中心线. https://ggplot2.tidyverse.org/reference/position_dodge.html

geom_curve并且arrow
还可以绘制具有曲线的线条,以便可以解决上述问题.然而,弯曲的部分很难观察一个图中的运动.虽然我改变了它的风格,箭头的形状并不尖锐,箭头也很难看到方向.

color=variable而position=dodge
我也试图spread/gather在df获得新的变量direction,并删除OD-对方向相反,这样我想我可以很容易地使用闪避段color=direction和position=dodge中ggplot2,但它没有工作(段仍然重叠).小例子如下所示.

O   D trip  direction    lon.x   lat.x    lon.y   lat.y
1   2  971  clock     697746.6 9312405 696929.6 9311051
2   1  300  anticlock 696929.6 9311051 697746.6 9312405
4   6  416  clock     696748.8 9308338 694906.4 9307087
4   7  621  anticlock 694906.4 9307087 696748.8 9308338

我非常感谢您的想法,以获得精心设计的数字.
另请参阅下图以获得实际用途spider network.

Answer 1

您可以使用三角函数来计算偏移值，然后将其插入调用中ggplot()。下面是使用上面的数据集的示例。我不太清楚顺时针是什么意思，所以我输入了一个简单的虚拟变量。

# make a dummy "clockwise" variable for now
df$clockwise = df$O > df$D
# angle from coordinates of stations
df$angle = atan((df$lat.y - df$lat.x)/(df$lon.y - df$lon.x))
# offsets from cos/sin of orthogonal angle
# scale the distance of the offsets by the trip size so wider bars offset more
# offset them one way if the trip is clockwise, the other way if not clockwise
df$xoffset = cos(df$angle - pi/2) * df$trip/5 * (2 * df$clockwise - 1)
df$yoffset = sin(df$angle - pi/2) * df$trip/5 * (2 * df$clockwise - 1)

ggplot() +
  geom_segment(data = df, aes(x = lon.x + xoffset, y = lat.x + yoffset, xend = lon.y + xoffset, yend = lat.y + yoffset, size = trip, color = clockwise),
               alpha = 0.5, show.legend = TRUE) +
  scale_size_continuous(range = c(0, 5), breaks = c(300, 600, 900, 1200),
                        limits = c(100, 1200), name = "Person trips/day (over 100 trips)") +
  theme(legend.key = element_rect(colour = "transparent", fill = alpha("black", 0))) + 
  guides(size = guide_legend(override.aes = list(alpha = 1.0))) +
  geom_point(data = df, aes(x = lon.x, y = lat.x), pch = 16, size = 2.4) +
  coord_fixed()